You asked for one that hasn’t been made. Don’t have a suggestion for one.
Some that have been made that make millions and could easily be recreated.
Non-profit/Fundraiser
There is a local guy who owns 7 planes and only flies one regularly. He makes his money from this area. The non-profit side gets a huge percentage of the donations for service fees, i.e. the cost of making your money do good for other people. His fundraiser side gets a percentage from the products he sells people who need to then resell for fund raising. All together it works.
Porn
Obviously makes money. But in order to get a foot in an already huge market, you’d have to supply content. Or alternately you could set up an elaborate network of referral sites (pay-per-click-through or similar) where your content is just purchased stock photos. There are several groups out there that do just this and do well. It seems like they are limited to the size their network however.
Religion/Self-Help
Combined, the two make plenty of people rich. It’s one of the largest pseudo-religious markets. And you can bet on people feeling bad about themselves so as long as you offer “help” you’ll have customers. Think Anthony Robbins, Joyce Meyer, Joel Osteen and the like. This could fit into a category that doesn’t exist, sort of… Most people currently go on tour as opposed to just having a website.
The only one out of the three that seems to be self-sustaining is the Porn referral thing or something similar such as ringtones or any other viral/compulsion market. Where the existence of the site is what you are making money on, not necessarily the content. Everything else requires constant research and addition to content.
You could mix television and the internet and make money. Find a good referral program, set up a site for it and advertise the site on television. You’ll annoy the majority of your country by creating the ad spots (think CrazyFox). The percentage of people that fall for that type of advertising is low but it doesn’t matter. Even with a low percentage you are still looking at millions of people hitting your site which refers them to the original.
Of course these are only ideas. I’m not for or against any of them necessarily.